Production of matrix metalloproteinases 2 and 3 (stromelysin) by stromal cells of giant cell tumor of bone.

Matrix metalloproteinases play a central role in the catabolism of extracellular matrix macromolecules. Here the authors report that giant cell tumor of bone (GCT) produces two matrix metalloproteinases (MMPs) in zymogen form, which have been identified as proMMP-2 (also known as "72-kDa-progelatinase/type IV procollagenase") and proMMP-3 (prostromelysin). Giant cell tumor is known to consist of two major cell populations, multinucleated giant cells and stromal cells. On several passages of the tumor cells in culture, only stromal cells proliferated. These stromal cells produced proMMP-2 but not proMMP-3. Addition of the conditioned medium of primary GCT culture or human macrophage-conditioned medium to the passaged stromal cells induced the production of proMMP-3. The production of proMMP-3 was also induced by interleukin 1 (IL-1), but not by tumor necrosis factor alpha (TNF alpha). ProMMP-1 (tissue procollagenase) was not detected even after treatment with these stimuli. Immunohistochemical studies have demonstrated that multinucleated giant cells in GCT both produce IL-1 and TNF alpha, suggesting that IL-1 secreted by multinucleated giant cells may be responsible for in vivo production of proMMP-3 by the stromal cells. The authors propose that GCT has a self-stimulatory system for the production of matrix-degrading proteinases and that the ability of the passaged stromal cells to synthesize and secrete proMMP-3 with appropriate stimuli may contribute the malignant behavior of GCT.